Apparatus for driving multi-light emitting devices
View Patent ↗An apparatus for driving multi-light emitting devices that drives a multi-channel light emitting unit having a plurality of light emitting channels connected in parallel with each other, each of which has a plurality of light emitting devices connected in series with each other according to an aspect of the invention may include: a DC/DC converter generating a driving voltage; a current control unit having a plurality of current sources connected between cathodes of the plurality of light emitting channels and a ground; a minimum voltage selection unit detecting a minimum detection voltage among the plurality of detected voltages at the cathodes of the plurality of light emitting channels; a first error detection unit detecting an error voltage determined by the difference between the minimum detection voltage and a predetermined first reference voltage; and a feedback coupling unit supplying the input voltage according to the error voltage and the driving voltage.
1. An apparatus for driving a multi-channel light emitting unit including a plurality of light emitting channels connected in parallel with each other, each of the light emitting channels including a plurality of light emitting devices connected in series with each other, the apparatus comprising:
a DC/DC converter configured to generate a driving voltage based on an input voltage and supply the driving voltage to an anode of the multi-channel light emitting unit;
a current control unit including a plurality of current sources connected between cathodes of the light emitting channels and a ground, and configured to keep currents flowing through the light emitting channels constant;
a minimum voltage selection unit configured to detect voltages at the cathodes of the light emitting channels and detect a minimum detection voltage among the detected voltages;
a first error detection unit configured to detect an error voltage corresponding to a difference between the minimum detection voltage and a predetermined first reference voltage; and
a feedback coupling unit configured to couple an output of the first error detection unit and an input of the DC/DC converter and supply the input voltage according to the error voltage and the driving voltage of the DC/DC converter, wherein
the light emitting devices are light emitting diodes, and
the first error detection unit comprises a first comparator having a non-inverting input terminal for receiving the minimum detection voltage, an inverting input terminal for receiving the first reference voltage, and an output terminal for outputting the error voltage.
2. An apparatus for driving a multi-channel light emitting unit including a plurality of light emitting channels connected in parallel with each other, each of the light emitting channels including a plurality of light emitting devices connected in series with each other, the apparatus comprising:
a DC/DC converter configured to generate a driving voltage based on an input voltage and supply the driving voltage to an anode of the multi-channel light emitting unit;
a current control unit including a plurality of current sources connected between cathodes of the light emitting channels and a ground, and configured to keep currents flowing through the light emitting channels constant;
a minimum voltage selection unit configured to detect voltages at the cathodes of the light emitting channels and detect a minimum detection voltage among the detected voltages;
a first error detection unit configured to detect an error voltage corresponding to a difference between the minimum detection voltage and a predetermined first reference voltage; and
a feedback coupling unit configured to couple an output of the first error detection unit and an input of the DC/DC converter and supply the input voltage according to the error voltage and the driving voltage of the DC/DC converter, wherein
the light emitting devices are light emitting diodes, and
the feedback coupling unit comprises:
a first MOS transistor having a drain connected to an operating power supply terminal, a gate connected to the output of the first error detection unit, and a source connected to the input of the DC/DC converter;
a first resistor connected between an output of the DC/DC converter and the input of the DC/DC converter;
a second resistor connected between the input of the DC/DC converter and a ground; and
a third resistor connected between the source of the first MOS transistor and the ground.
3. An apparatus for driving a multi-channel light emitting unit including a plurality of light emitting channels connected in parallel with each other, each of the light emitting channels including a plurality of light emitting devices connected in series with each other, the apparatus comprising:
a DC/DC converter configured to generate a driving voltage based on an input voltage and supply the driving voltage to an anode of the multi-channel light emitting unit;
a current control unit including a plurality of current sources connected between cathodes of the light emitting channels and a ground, and configured to keep currents flowing through the light emitting channels constant;
a minimum voltage selection unit configured to detect voltages at the cathodes of the light emitting channels and detect a minimum detection voltage among the detected voltages;
a first error detection unit configured to detect an error voltage corresponding to a difference between the minimum detection voltage and a predetermined first reference voltage; and
a feedback coupling unit configured to couple an output of the first error detection unit and an input of the DC/DC converter and supply the input voltage according to the error voltage and the driving voltage of the DC/DC converter, wherein
the minimum voltage selection unit comprises:
a first minimum voltage selector configured to select a first minimum voltage among some of the detected voltages; and
a second minimum voltage selector configured to select the minimum detection voltage among the rest of the detected voltages and the first minimum voltage from the first minimum voltage selector.
4. An apparatus for driving a multi-channel light emitting unit including a plurality of light emitting channels connected in parallel with each other, each of the light emitting channels including a plurality of light emitting devices connected in series with each other, the apparatus comprising:
a DC/DC converter configured to generate a driving voltage based on an input voltage and supply the driving voltage to an anode of the multi-channel light emitting unit;
a current control unit including a plurality of current sources connected between cathodes of the light emitting channels and a ground, and configured to keep currents flowing through the light emitting channels constant;
a minimum voltage selection unit configured to detect voltages at the cathodes of the light emitting channels and detect a minimum detection voltage among the detected voltages;
a first error detection unit configured to detect an error voltage corresponding to a difference between the minimum detection voltage and a predetermined first reference voltage; and
a feedback coupling unit configured to couple an output of the first error detection unit and an input of the DC/DC converter and supply the input voltage according to the error voltage and the driving voltage of the DC/DC converter, wherein
the minimum voltage selection unit comprises first to n-th minimum voltage selectors each for selecting a minimum voltage among the detected voltages in each of first to n-th groups into which a plurality of detection voltage terminals corresponding to the light emitting channels are divided, each group including a predetermined number of detection voltage terminals,
the first minimum voltage selector is configured to select a first minimum voltage among the detected voltages of the first group,
the second minimum voltage selector is configured to select a second minimum voltage among the detected voltages of the second group and the first minimum voltage from the first minimum voltage selector, and
the n-th minimum voltage selector is configured to select the minimum detection voltage among the detected voltages of the n th group and an (n- 1 ) th minimum voltage from the (n- 1 ) th minimum voltage selector.